word-perfect 
(North American also letter-perfect)
adjective
(Of an actor or speaker) knowing by heart the words for one’s part or speech: Burton arrived at the first rehearsal word-perfect...
- He honed scripts until they were word-perfect and thwarted actors’ attempts to ad lib or modify the text.
- He sang his song, accurately, word-perfect, that's all.
- Despite the difficulties of putting a performance together over the festive period, the cast was word-perfect on the first night, their comic timing spot-on and the production pacey.
